1. Field of the Invention
This invention relates to foam regulators particularly suitable for use in surfactant-containing compositions, comprising a mixture of paraffin hydrocarbons and hydrophobic silica. 2. Statement of the Related Art
Paraffin hydrocarbons have already been repeatedly proposed as foam regulators for detergents and cleaners. According to British patent specification No. 1,099,502 and corresponding German patent application No. 14 67 699, the hydrocarbons are dispersed in aqueous, soap-containing detergent slurries and the resulting dispersion subsequently spray dried. In this process, however, a large part of the foam-inhibiting effect is lost. To correct that loss, it is necessary to use comparatively large quantities of paraffin, which results in a reduction in detergency. Accordingly, German patent application No. 14 67 614 proposes adding the paraffins to the washing powder after spray drying so that they form agglomerates with the detergent particles. However, the foam-inhibiting effect depends in this case, too, upon the presence of soap which confines the possible formulations to soap-containing mixtures.
U.S. Pat. No. 4,056,481 and corresponding German patent application No. 25 00 411 describe foam-regulated detergents which contain from 0.02 to 8% of a wax or wax mixture having a melting range of 35.degree. to 125.degree. C. The wax component, which preferably consists of microcrystalline waxes, is supposed to be present in intimate admixture with the surfactant component of the detergent. It can be shown that preparations such as these are virtually ineffectual with respect to anionic surfactants. In addition, known silicone defoamers may be added to the described preparations, as disclosed in Canadian Pat. No. 1,039,142 and corresponding German patent application No. 25 09 508. Particulate defoaming quantities of from 5 to 15% by weight, and from 0.5 to 2.1% of defoamer are required for adequate foam damping, which must be regarded as a disadvantage in view of the fact that paraffin hydrocarbons and waxes, similar to greasy stains, inhibit the cleaning effect of a detergent.
Preparations containing from 0.25 to 35% of wax, particularly microcrystalline wax, from 65 to 99.75% of nonionic surfactants and, as an optional constituent, silicones or silanized silica are the subject of British patent application No. 1,560,076, and corresponding German patent application No. 26 50 365. The foam-inhibiting effect of these mixtures is again largely confined to nonionic detergents. The same disadvantage attends the detergents according to European patent application No. 8,829 which contains from 3 to 30% of predominantly nonionic surfactants, from 10 to 96.9% of builder salts and from 1 to 5% of a defoamer. This defoamer consists of a homogenous dispersion of nonionic surfactants, silanized silica and paraffin or microcrystalline waxes melting at 35.degree. to 110.degree. C. and is applied to the preformed detergent particles in mixers.
U.S. Pat. No. 4,363,740 and corresponding European patent application No. 45,208 describe granular defoamers which are obtained by spraying a known meltable defoamer, preferably a paraffin wax, onto a granular base material. The temperature of the granular base material should be at least 15% below the solidification point of the defoamer. The granulates are preferably used in detergents and cleaners. It can be shown that defoamer mixtures of complex composition lead to non-reproducible results where this procedure is adopted.
U.S. Pat. No. 4,192,761 and corresponding German patent application No. 28 57 155, are of particular interest so far as the present invention is concerned, describing a detergent composition containing from 0.01 to 5% of a foam inhibitor. From 99.9 to 75% of this inhibitor consists of a mixture of a hydrocarbon liquid at room temperature with a solid hydrocarbon or wax ester, i.e. one melting at 35.degree. to 100.degree. C., and 0.1 to 25% of a hydrophobic (silanized) silica. The ratio in which the liquid and solid hydrocarbons are mixed is disclosed as between 30:70 and 98:2. The detergent component to be defoamed may consist of anionic and/or nonionic surfactants. Where anionic detergents are present in quantities of from 5 to 15% by weight, from 0.5 to 2.1% of defoamer are required for adequate foam damping, which must be regarded as a disadvantage in view of the fact that paraffin hydrocarbons and waxes, similar to greasy stains, inhibit the cleaning effect of a detergent.
U.S. Pat. No. 3,388,073 describes foam inhibitors for aqueous latex emulsions, paper pulp, and the like, there being no mention of detergent compositions. The inventive compounds disclosed are dialkyl substituted cyclic siloxanes, which are preferably dispersed in aliphatic hydrocarbon oils. The oils may include mineral seal oil and paraffin waxes, and are present in an amount of 60 to 99%.